It's (to me) more plausible that they are just incompetent and lack the manpower/skills to produce more units at a faster pace. Again, just my opinion.
Really, once they had the designs ready, why didn't they have the units built in China instead of making themselves? It's like Apple making iPhones themselves, by the time the iPhone 5 was announced they'd still be working on the backlog of iPhone 4 orders.
Funny how Google/Motorola mange to make the Moto-X in Texas
If you want to support US workers you now have a choice!
http://www.theverge.com/2013/9/11/4717796/made-in-america-a-look-inside-motorolas-moto-x-factory